Alignment method

Abstract

An alignment method in which a plurality of areas on a wafer which are to be exposed are each aligned with respect to a reference position. The method includes: measuring array coordinates of a plurality of alignment measuring points; determining a reliability value for each alignment datum on the basis of a dispersion of differences (alignment data) between the measured array coordinates and the corresponding design values; calculating values of coordinate transformation parameters for obtaining actual array coordinates from the design array coordinates by using the reliability value as a weight; and obtaining array coordinates of each shot area by using the transformation parameters.

What is claimed is: 
     
       1. An alignment method for aligning a plurality of exposure areas on a substrate, said method comprising the steps of: (1) measuring array coordinates of a plurality of alignment marks which are associated with N (N is an integer of 3 or more) exposure areas among said plurality of exposure areas on said substrate;   (2) determining a reliability value for each of the array coordinates measured at said step (1), the i-th (i is an integer from 1 to N) reliability value being determined on the basis of (a) the measured results of (N-1) array coordinates from which the measured result of the i-th array coordinate is excluded, and (b) design array coordinates on said substrate;   (3) obtaining actual array coordinates of said plurality of exposure areas on the basis of said design array coordinates, said array coordinates measured at said step (2) and the reliability value determined at said step (2); and   (4) sequentially aligning each of said plurality of exposure areas on the basis of the actual array coordinates obtained at said step (3).   
     
     
       2. The alignment method according to claim 1, wherein said step (2) obtains said i-th reliability value from a dispersion of (N-1) non-linear errors excluding the measured results of said i-th array coordinate. 
     
     
       3. The alignment method according to claim 2, wherein the reliability value having a small dispersion is less than the reliability value having a large dispersion. 
     
     
       4. The alignment method according to claim 1, further including the step of weighting said determined reliability value. 
     
     
       5. The alignment method according to claim 1, wherein said alignment method is used in a lithography process for manufacturing at least one of semiconductor devices and liquid crystal display devices. 
     
     
       6. The alignment method according to claim 1, wherein said alignment method is performed by using an alignment sensor of an image pick-up type which picks up images of said alignment marks and processes the images. 
     
     
       7. The alignment method according to claim 1, wherein said alignment marks are provided in respective centers of said desired number of exposure areas. 
     
     
       8. The alignment method according to claim 1, wherein the measurement of the alignment mark for each of said desired number of exposure areas is carried out by measuring coordinate positions in directions of two coordinate axes perpendicularly intersecting each other. 
     
     
       9. The alignment method according to claim 1, wherein the measurement of the alignment mark for each of said desired number of exposure areas is carried out by selectively measuring a coordinate position in either one of directions of two coordinate axes perpendicularly intersecting each other. 
     
     
       10. An alignment method for aligning a plurality of exposure areas on a substrate placed on a substrate stage, said method comprising the steps of: (1) measuring array coordinates of a plurality of alignment marks which are associated with N (N is an integer of 3 or more) exposure areas among said plurality of exposure areas on said substrate;   (2) determining a reliability value for each of the array coordinates measured at said step (1), the i-th (i is an integer from 1 to N) reliability value being determined on the basis of (a) the measured results of (N-1) array coordinates from which the measured result of the i-th array coordinate is excluded and (b) design array coordinates on said substrate;   (3) obtaining a plurality of transformation parameters which transform said design array coordinates into array coordinates on said substrate stage on the basis of the reliability value determined at said step (2);   (4) obtaining actual array coordinates of said plurality of exposure areas on the basis of said plurality of transformation parameters; and   (5) sequentially aligning each of said plurality of exposure areas on the basis of the actual array coordinates obtained at said step (4).   
     
     
       11. The alignment method according to claim 10, wherein said step (2) obtains said i-th reliability value from a dispersion of (N-1) non-linear errors excluding the measured results of said i-th array coordinate. 
     
     
       12. The alignment method according to claim 11, wherein the reliability value having a small dispersion is less than the reliability value having a large dispersion. 
     
     
       13. The alignment method according to claim 10, further including the step of weighing said determined reliability value. 
     
     
       14. The alignment method according to claim 10, wherein said alignment method is used in a lithography process for manufacturing at least one of semiconductor devices and liquid crystal display devices. 
     
     
       15. The alignment method according to claim 10, wherein said alignment marks are provided in respective centers of said desired number of exposure areas. 
     
     
       16. The alignment method according to claim 10, wherein the measurement of the alignment mark for each of said desired number of exposure areas is carried out by measuring coordinate positions in directions of two coordinate axes perpendicularly intersecting each other. 
     
     
       17. The alignment according to claim 10, wherein the measurement of the alignment mark for each of said desired number of exposure areas is carried out by selectively measuring a coordinate position in either one of directions of two coordinate axes perpendicularly intersecting each other. 
     
     
       18. An alignment method for aligning each of a plurality of exposure areas on a substrate, said method comprising the steps of: (1) measuring array coordinates of a plurality of alignment marks which are associated with N (N is an integer of 3 or more) exposure areas among said plurality of exposure areas on said substrate;   (2) determining a reliability value for each of the array coordinates measured at said step (1), the i-th (i is an integer from 1 to N) reliability value being obtained by estimating the i-th array coordinate by a linear approximation calculation using (a) the measured results of (N-1) array coordinates from which the measured result of said i-th array coordinate is excluded and (b) design array coordinates on said substrate, and by obtaining a magnitude of the difference between said estimated i-th array coordinate and said i-th array coordinate measured at step (1), wherein said reliability value being obtained is inversely proportional to the magnitude of the difference;   (3) obtaining actual array coordinates of said plurality of exposure areas on the basis of said design array coordinates, said array coordinates measured at said step (1) and the reliability value determined at said step (2); and   (4) sequentially aligning each of said plurality of exposure areas on the basis of the array coordinate obtained at said step (3).